Very good spot about SPG
Details here:
https://www.britishairways.com/trave...club/_gf/en_gb
$560 is currently £348. 20k SPG = 25k BA = 31,250 BA Miles with the extra 25%. That is just 1.1p per mile and is certainly attractive. If you factor in an extra 696 miles for doing the purchase on the Amex Gold, you are down to 1.09p.
If the $ goes into a dive over the next few weeks after the Fed starts QE again, you may even get close to 1p.